Enma Daiō is the sovereign ruler and head judge of Jigoku, the Japanese underworld, within the universe of GeGeGe no Kitarō. His role is to determine the final destination of souls, deciding which realm of hell they are sent to based on the nature and severity of their sins committed during their lifetime. He is a figure of immense authority who maintains the balance between the human world and the supernatural realm.

In terms of appearance, Enma Daiō is consistently presented as a formidable and imposing figure. He is often depicted as a large man with red skin, wild black hair, and a fearsome face featuring prominent fangs. His typical attire resembles the robes of a traditional Tang Dynasty official, though the specific design of his clothing and his overall size can vary significantly across different series and films. He has the ability to change his physical size at will, ranging from a normal human stature to that of a towering giant. In the specific film GeGeGe no Kitarō: Sennen Noroi Uta, known in English as Kitaro and the Millennium Curse, he possesses a distinct design that includes a proportionally larger head and a pair of horns.

The personality of Enma Daiō is defined by his role as a divine judge. He is often portrayed with a loud, booming, and authoritative voice, and he can display a terrifying anger, especially towards those who disrupt the natural order or commit great evil. His wrath is said to be powerful enough to summon thunderclouds and unseasonal rain. Despite this fearsome exterior and his status as the king of hell, his actions are not typically malicious or arbitrary. Instead, he acts as an impartial arbiter of cosmic law, punishing evil and maintaining order. He is known to observe the deeds of humans and can dispatch yōkai to deal with wicked individuals. Enma Daiō is also aware of the destructive potential of his own divine power and generally refrains from direct intervention in the living world to avoid causing massive collateral damage.

Enma Daiō’s motivations are inherently tied to his function as a ruler of the afterlife. He is driven to preserve the integrity of the cycle of reincarnation and the judgment system of hell. In the Kitaro and the Millennium Curse narrative, his role is consistent with this overarching duty. He serves as a distant but powerful authority figure. His key relationships are primarily with the yōkai world, communicating directly with spirits like Kitarō through dreams or by projecting his image across great distances. He also has a connection to Medama Oyaji, Kitarō's father, which allows for communication and access to the underworld when necessary.

As a character, Enma Daiō does not typically undergo significant personal development, as he represents a constant, mythologically-rooted force. However, his power and his role as a final arbiter are central to the plot. His judgments and the deals he strikes with the main characters can have immense consequences. For example, in one storyline, he makes a pact with Kitarō, offering to break a natural law in exchange for a dangerous mission. This demonstrates that while he is a judge, he is also capable of pragmatic and transactional interactions that drive the story forward.

His notable abilities are vast and reflect his divine status. As the ruler of Jigoku, he can manipulate the process of reincarnation, deciding where and when a soul will be reborn. He is powerful enough to single-handedly support the weight of all of hell. In combat, he can emit destructive green energy beams from his eyes and summon a naginata, a type of Japanese polearm, to wield. He is also a master of Jigoku's Ultimate Secret Art, a set of techniques that allow him to unleash the powers of hell without any external keys or artifacts. Furthermore, he can command and send other yōkai as his agents to the living world. In the Kitaro and the Millennium Curse film specifically, he demonstrates his power over nature by manipulating clouds to send messages from the underworld to the living realm.